Method for calibrating a multi-channel radio receiver

A computer-implemented method of calibrating a receiver comprising a plurality of analog reception channels, each including an antenna element of a multi-element antenna, the plurality of analog reception channels comprising a reference channel, the computer-implemented method comprising:

• determining, for each analog reception channel other than the reference channel of the plurality of analog reception channels, a phase shift with the reference channel,
• wherein the determining comprises:
• calculating an observed covariance matrix representative of a covariance between pairs of a series of samples of one or more reference radio signals incident on the multi-element antenna, the pairs of the series of samples being collected in parallel on each analog reception channel of the plurality of analog reception channels over a period of time,
• obtaining an estimate of a reference covariance matrix representative of a covariance between pairs of series of samples of said one or more reference radio signals which would be collected in parallel on each analog reception channel of the plurality of analog reception channels over the period of time in the absence of a phase shift between the analog reception channels,
• calculating a product matrix, resulting from a term-by-term matrix product of the observed covariance matrix with the estimate of the reference covariance matrix;
• and
• determining an argument of complex terms of the product matrix, and
• correcting, for each analog reception channel other than the reference channel of the plurality of analog reception channels, the phase shift with the reference channel, based on the argument of the complex terms of the product matrix.